Free adaptive tessellation strategy of bézier surfaces

[Abstract] Rendering of Bézier surfaces is currently performed by tessellating the model on the GPU and rendering the highly detailed triangle mesh. Whereas non-adaptive strategies apply the same tessellation pattern to the whole surface resulting in a uniform tessellation of the patch, adaptive approaches make it possible to reduce the number of triangles generated without a loss of quality. However, the most usual approaches to adaptive tessellation have little flexibility and do redundant computations and memory accesses, as each sample is independently evaluated in the Domain Shader of the DirectX11 pipeline. In this paper an adaptive tessellation technique based on the exploitation of the spatial coherence data within each surface is presented. The GPU implementation of this technique is simple and efficient and, as consequence, the tessellation of complex models can be performed in real-time. The analysis of the GPU performance and limitations for different adaptive degree of the tessellation performed suggest innovations in future graphics card generations for supporting a larger degree of adaptivity without a penalty

Efficient Culling Techniques for Interactive Deformable NURBS Surfaces on GPU

[Abstrtact] InfoValue: NURBS (Non-uniform rational B-splines) surfaces are the standard freeform representation in Computer-Aided Design (CAD) applications. Rendering NURBS surfaces accurately while they are interactively manipulated and deformed is a challenging task. In order to achieve it, the elimination from pipeline in early stages of back-facing surfaces or surface pieces is a key advantage. Furthermore, an effective interactive manipulation implies that all the culling computations should be performed for each frame, facing the possibility of fast changes in occlusion information. In this paper, different interactive culling strategies for NURBS surfaces are presented and analyzed. These culling techniques are based on the exploitation of the geometric properties presented in a NURBS surface, that allow easily to find bounds for it in screen space for each frame. Furthermore, the culling overhead for our proposals is small compared to the computational saving, outperforming a proposal without culling. An implementation of these strategies using current GPUs is presented, achieving real-time and interactive rendering rates of complex parametric models.Xunta de Galicia y fondos FEDER; GRC2013/055Ministerio de Economía y Competitividad y fondos FEDER; TIN2013-42148-

Culling Techniques for Deformable NURBS Surfaces

[Resumo]: As superficies NURBS son unha representación estándar de modelos que se usan normalmente en deseño asistido por ordenador (CAD), enxeñaría naval, enxeñaría de automóbiles ou imaxes procesadas para uso médico. Adicionalmente estas ofrecen moitas vantaxes, debido a que con pequenas modificacións nalgúns puntos de control resultan en modelos moi complexos. No entanto, non hai garantía de obter un nivel suficientemente alto de teselación para evitar modelos con redes toscas, polo que no seguinte proxecto describiranse o uso de diferentes técnicas de culling, que axudarán a reducir o cómputo innecesario de superficies non visibles e en consecuencia a obter un mellor rendemento con menos artefactos.[Abstract]: NURBS surfaces are a standard representation of models typically used in computer-assisted design (CAD), naval engineering, car engineering, or medical-processed images. Furthermore, NURBS surfaces have many advantages, a small modification on some control points result in highly complex models. However there is no guarantee of obtaining an high enough level of tessellation in order to avoid coarse models, which is why in the following project it will be described the use of different culling techniques that might help to reduce the unnecessary computation of no visible surfaces and in consequence the achievement of a better performance with fewer artefacts.Traballo fin de grao (UDC.FIC). Enxeñaría Informática. Curso 2022/202

Meshless Animation Framework

This report details the implementation of a meshless animation framework for blending surfaces. The framework is meshless in the sense that only the control points are handled on the CPU, and the surface evaluation is delegated to the GPU using the tessellation shader steps. The framework handles regular grids and some forms of irregular grids. Different ways of handling the evaluation of the local surfaces are investigated. Directly evaluating them on the GPU or pre-evaluating them and only sampling the data on the GPU. Four different methods for pre-evaluation are presented, and the surface accuracy of each one is tested. The framework contains two methods for adaptively setting the level of detail on the GPU depending on position of the camera, using a view-based metric and a pixel-accurate rendering method. For both methods the pixel-accuracy and triangle size is tested and compared with static tessellation. Benchmarking results from the framework are presented. With and without animation, with different local surface types, and different resolution on the pre-evaluated data